Wow, talking about endorsement! No pressure right? 😀
I was online a tad less the last few weeks due to some physical issues (nothing life-threatening!).
On-topic: First question that comes to mind is that there is a beta-version of appleOS (as OSX is now called) out there, which specifically deals with the touchbar. I’ve heard other stories of DJ Software (like Mixvibes Cross) going AWOL there with other controllers. While initially thinking that the beta software was to blame (which it usually is if things that worked, suddenly don’t work anymore), now I am starting to wonder if there isn’t a link to the actual (touchbar) hardware.
Unless, of course, you ARE using that beta.
Do you have another (brand/model) controller you can borrow to try and see if it crashes Serato as well? If it does, that will at least eliminate hardware failure from the equation. Mind you, if things go wrong when changing something in your setup, the last thing changed is usually where the problem lies. While possible (Murphy is almighty), it is far less likely that your hardware decided to breakdown at exact the same moment you swapped out some gear.
Over at the Denon site there are some posts, including some settings for the 8000 you could check. Lots of problems seem to occur on the midi front. While you can change the latency in Serato you can (also) change it in the 8000. It’s worth to have a look at that too.
Hope that helps a bit in the right direction. Let us know how you fare.